Reviving the PoE++ Feature on a Ubiquiti Switch

What happened

Using a PoE splitter it was confirmed that the PoE functionality was indeed dead. Recently [The Parallel Port] was asked to take a look at repairing the PoE++ feature on a Ubiquiti switch that otherwise worked fine.

With power applied the switch starts up as normal, including its 1.3″ touch screen that provides direct port information as well as a fancy screensaver cum QR code for the AR feature. After disassembly and some testing with a multimeter and thermal camera, a short and related hot spot on the PCB that the PoE power board connects to was identified, with the short persisting after removing this PCB from the switch.

Since the switch had suffered a bit of an electrical event the TVS diode was checked, but it turned out to be fine. Next to it, marked as fuses, were protective thyristor surge protection devices ( Trisil ), functioning as a crowbar device.